Vacuum-tube circuits



- 1,503,709 H. M. PRUDEN VACUUM TUBE CIRCUITS 30 Filed Afiril s, 1923 I a a QUG 0| I i b fl w ny.

Patented Apg S, i924.

UNITED STATES PATENT-OFFICE.

HAROLD M. PRUDEN, OF EAST ORRAINGE, NEW JERSEY, ASSIGNOR-TO WESTERN ELEC- TRIO OOZMIAN Y, INCORPORATED, OF NEW YORK, N. Y., A COEBPORATION. OF NEW YORK.

Application filed April 3,

To all whom it may concern: Be it known that I, HAROLD M. PRUDEN, a citizen of the United States, residing 'at East Orange, inthe county of Essex, State of New Jersey, have invented certain new and useful Improvements in Vacuum-Tube Circuits, of which the following is a full, clear, concise, and exact description. 7

This invention relates to circuits 'for supplying electric energy to vacuum tubes and has for an object toprovide for the continuous flow of heating current home common source through a plurality of vacuum tube cathodes when one or more of the cathodes become broken or otherwise removed from the circuit. c p i a In accordance with the invention the filamentarycathodes of a plurality of vacuum tubes are connected in series with a common battery or othersource of potential and a three-winding relay is associated with each of the cathodes. One of the windin' has a high resistance is connected 1n shunt to the cathode. When the corresponding cathode is burned out or otherwise removed,

this winding carries sufiicient current to op-- erate an armature connecting in shunt a second'winding having approximately the resistance of the "filament which it replaces. The magnetic flux produced by the second winding is additive to that produced by the first and insures holding the armature in closed position. A third-winding in series with the cathodeis so arranged as to pro? duce a flux opposing the flux produced by the first two wmdings and causes the armatime to be released when the filament has been replaced or otherwise reconnectedin the c1rcuit.' I fi A further object of the invention .1s to apply the proper grid or control electrode potentials to a plurality of tubes having a common heating circuit.

The invention will be more fully understood from the following detailed descrip tion and claims taken in connection with the accompanyin drawin in which the figure represents scematica y a system embodyin theinvention.

I eferrin tothe drawing by reference numerals t e three-electrode vacuum tubes 1, 2, 3 and 4 are representative of a series of .detectors which are employed in se arate signaling circuits, respectively. Eac vacuum tube contains a cathode 8,'a grid or convacuum-roan cmcnrrs,

1923. Serial no. 629,566.

-In one installation the battery 15-was a 24 volt battery such as is commonly employed in a telephone oflice and eight filaments were connected in series therewith, four only being shown in the drawing. 'T he circuit may be traced as follows: From ground throughbattery 15, an automatic-' current regulator 17; the use of whichis optional, contact 18', and through a network having three paths in'parallel, one comprising the winding 19' which 5 of a relaj 20,- a contact 22, and the cathode 8 of the vacuum tube 1', the second comprising a high resistance, the winding 24 of relay 20, and the third comprising resistances 25 and 26. v The resistance of the seoondand third of these paths is suficiently high "that most of the current flows through the oathode 8, the circuit then continues through similar networks for each of the vacuum tubes 2, 3, 4, etc., to ground at 27.

The anodes 10 of the respective tubes are connected in parallel with a source of poten tial 30. The ener ation of the respective I tubes is controlle by keys 31, contacts 32 closing the anode circuits. The contacts 33 connect ground through a common: relay 34:

which in turn closes contact 18. The con-' tact 35 connects ground to relay 36 which closes contact 22 in series with the corre-p sponding vacuum tubes. Relay 36 also closes contact 37 which is in series with contact 38.

When one ofthe filaments 8 is burned out current ceases to flow in winding 19 and at the same time the current-is increased in winding 24- and armature 39 is drawn up connecting the winding 40 in a fourth'path in parallel to the three above described. The winding 40 has approximately the resistance of one of the cathodes 8" plus the resistance of the corresponding winding 19 and permits the proper amount of current" 46. When the damaged tube has been replaced, current again flows in the winding 19 and the currents through windings 24 and 40 are decreased. Contacts 38 and 39 are opened and the circuit isagain in the condition shown in the drawing.

When one of the keys 31 is opened for the purpose of deenergizing the corresponding vacuum tube, contact 22- is opened and rela 20 acts as above described to substitute winding 40 for the filament. The lamp 42 and alarm 46, however, are not energized for the reason that contact 37 is open.

Negative grid potential for the tubes 1 and 2 is'obtained by means of batteries inserted in series with the secondaries of the input transformers. In one installation employing this circuit, batteries were available in units somewhat larger than the required difference of potential between the negative terminal of the filament the grid. It was found possible to so proportion the resistances 25 and 26* that the potential of battery 50 minus the drop in resistance 25, gave a suitable grid voltage for each of tubes 1 and 2, and the drop in the filament of tube 2 plus the drop in the resistance 26 associated with tube 1, gave substantially the required voltage t the grid of tube 3. The'grid circuits of each tube after the first two, therefore comprise a conductor 52 connected between resist ances 25 and 28' oi'the second preceding tube. a

While only one embodiment of the invention has been described, it is apparent that the-invention may be used in other circuits and may be apphed thereto in a variety of ways within the scopeof the appended claims.' 4 i The invention cla med is:

incense ments, means for connecting said filaments in series with a source of heating current, and a three winding relay associated With one of said filaments, one of said windings being efiectively in shunt to said filament,

another of said windings being opposed to said first winding and 'being in series with said filament, and the third of said Windings being arranged to aid said first winding and having a resistance corresponding to that of said filament, said relay havin a contact for closing the circuit of said third winding when the current through said second winding is reduced.

3. In combination, a plurality of filaments, means for connecting said filaments in series with a source of heating current, and a three Winding relay, one winding of said relay having a resistance corresponding to the resistance of one-of said filaments, said relay having a contact for closing the circuit of said winding when said filament is broken, and a contact for operating an alarm. 1

4. In combination, a plurality. of three electrode vacuum tubes having their filaments connected in series, a resistance path in shunt to one of said filaments, a connection comprising a battery from a point intermediate the terminals of said path to the grid corresponding to said filament and a normally unipotential connection from said point to another control electrode.

In witness whereof, I hereunto subscribe my name this 2nd day of April A. 1)., 1923.

' nAno nn. PRUDEN. 

